bio112 ch18 flashcards

What is evolution?

Evolution = species/populations change over time.

Who developed the idea of natural selection?

• Charles Darwin

• Alfred Wallace

What is required for natural selection?

There must be variation between individuals in a population.

What did Darwin notice about finches?

Finches had different beak shapes adapted to different food sources.

Different environment/food → favors different beaks.

What did Peter & Rosemary Grant discover about finches?

Beak size can change depending on environmental conditions.

• Lots of rain → small, soft seeds → smaller bills

• Larger seeds available → larger bills increase

Evolutionary change can happen slowly OR quickly.

What are the 3 principles of natural selection?

1. Inheritance
Traits are passed parent → offspring.

2. Overproduction
More offspring are produced than can survive because resources are limited.

3. Variation
Offspring have different heritable characteristics.

Where does genetic diversity come from?

• Mutations

• Sexual reproduction

Mutations can:

• ↓ fitness

• ↑ fitness

• have no effect

What is an adaptation?

A heritable trait that helps an organism survive and reproduce in its current environment

Arctic fox + ptarmigan turning white in winter is an example of what?

Adaptation due to similar selective pressures.

What is divergent evolution?

Related species evolve in different directions from a common point/ancestor.same origin → become DIFFERENT

What is convergent evolution?

Unrelated species independently evolve similar traits/functions.Example: bat wings vs. insect wings

What are major types of evidence for evolution?

• Fossils

• Homologous structures

• Vestigial structures

• Embryology

• Biogeography

• Molecular/DNA evidence

What are homologous structures?

Structures with similar underlying anatomy because organisms share a common ancestor.

They may have different functions today

What are vestigial structures?

Structures with little/no known current function that may remain from an ancestor.

Examples:

• Wings of flightless birds

• Hind bones in whales

How does embryology provide evidence for evolution?

Similarities during embryo development can show relatedness.

Example: vertebrates have gill slits and tails at some point during development.

How does biogeography provide evidence for evolution?

Where organisms live can reveal their evolutionary history.

How does molecular biology provide evidence for evolution?

More closely related organisms have more similar DNA sequences.

Is evolution “just a theory”?

No.

In science, a theory = a thoroughly tested and verified explanation supported by evidence.

Do individuals evolve?

No. Populations evolve.

Evolution = change in the average characteristics of a population over time

Does evolution explain the origin of life?

No.

Evolution explains how populations change and diversify over time, not how life originally began.

Do organisms evolve “on purpose”?

No.

Populations evolve in response to changing environmental conditions/selective pressures.

What is a species?

A group of organisms that can interbreed and produce:

fertile + viable offspring

What is a hybrid?

Offspring produced by organisms from different species.

Hybrid offspring may be infertile

What is speciation?

Formation of 2 species from 1 original species.

What is allopatric speciation?

Speciation caused by geographic separation.

Population gets physically separated → populations evolve independently.

ALLO = Apart

What is dispersal?

A few members of a species move to a new geographic location.

What is vicariance?

A natural event/barrier physically divides a population.

What is sympatric speciation?

New species form while populations remain in the same geographic location.

Can result from chromosomal errors during cell division.

SYM = Same place

Allopatric vs. sympatric speciation?

Allopatric → geographic separation 🗺

Sympatric → same location 📍

What is adaptive radiation?

One species spreads into different areas/niches → evolves into multiple different species.

What is aneuploidy?

Having too many or too few chromosomes because of nondisjunction during meiosis.

Can produce:

• 2n + 1

• 2n − 1

What is autopolyploidy?

Occurs when mitosis is not followed by cytokinesis.

What does the PPT describe as alloploidy?

Two species mate → viable offspring.

The slide’s example involves a normal gamete from one species + a polyploid gamete from another species.

What is a prezygotic barrier?

A reproductive barrier that prevents fertilization/zygote formation.

What are the 4 prezygotic barriers from the PPT?

1. Temporal → different breeding times

2. Habitat → different habitats

3. Behavioral → different mating behaviors

4. Gametic → gametes can’t successfully fertilize

What is temporal isolation?

Species reproduce at different times/schedules.

Example: two frog species breed at different times of year.

What is habitat isolation?

Populations occupy different habitats, so they don’t regularly encounter each other to reproduce.

What is behavioral isolation?

Differences in mating behavior prevent organisms from mating.

What is a gametic barrier?

Differences between gametes prevent fertilization.

What is a postzygotic barrier?

Barrier that occurs AFTER a zygote forms.

Possible outcomes:

• Embryo doesn’t survive

• Offspring survives but is sterile

What is gradual speciation?

Species change at a slow, steady rate.

What is punctuated equilibrium?

Rapid evolutionary change → followed by long periods of little/no change.